The CDC estimates that fluoridation now “reduces cavities by about 25% in children and adults.”

But there is compelling new evidence that fluoride delivered through tap water may not be the safest kind.

A study of 512 Canadian mothers and their children, published in the journal JAMA Pediatrics earlier this week, suggests that drinking fluoridated water during pregnancy could damage kids’ brains. In the study, boys between the ages of 3 and 4 years old whose mothers drank fluoridated water had slightly lower IQs (about 4.5 points lower, a small but noticeable difference when you consider that the average IQ score is around 100 points.)

But public health experts don’t suggest switching to bottled water just yet. That’s because a single study should never overturn years of scientific consensus about the health benefits of fluoridated water.

Why you don’t need to start drinking bottled water

“We really need to study this more carefully, study it in a US population, which has not been done,” Leo Trasande, a pediatrician and public-health researcher at NYU Langone Health told Business Insider. “In the big picture, I’m not suggesting people shift to bottled water over this issue. There are plenty of lower-hanging fruit here with respect to preventing exposures that disrupt thyroid hormone and ultimately affect brain development.”

Some of the easiest ways to ensure brain health in kids, Trasande said, are to make sure there’s enough fresh air circulating through your home, reduce your family’s exposure to pesticides, and make sure your kids are getting enough iodine in their diet through foods like iodized salt, seafood, and dairy.

Fluoride wasn’t purposefully added in to drinking taps until 1945, when the first fluoridation trials started in Grand Rapids, Michigan. Cavity rates quickly plummeted 60% there for kids who were born after fluoride was added to the water, and many other places around the globe quickly followed suit.

However, the dose of fluoride is important. Too much of the mineral can cause brown, pitty spots on kids teeth, a condition called fluorosis. As recently as 2015, recommendations for fluoride concentrations in US drinking water were lowered to 0.7 milligrams per liter.

There have been plenty of conspiracy theories lobbed at fluoridated water over the years, including the idea that fluoridation is a plot by the government to control our minds (it’s not) and that Nazis put fluoride in the water they served in WWII concentration camps ( again, no).

Fluoridated water may not be the best way to prevent cavities

This new study, if further evidence supports it, may give more scientific weight to the idea that fluoridated water is not the best route to prevent cavities. Fluoridated water enters the body and the bloodstream orally, whereas most toothpaste and fluoride treatments given at the dentist are spit back out.

These more topical routes for fluoride administration are “the best route for getting fluoride to the teeth,” Trasande said.

Stephen Peckham, a professor of health policy at the University of Kent wrote similarly with his co-authors that “artificial water fluoridation is not necessarily the most economical, effective, or affordable way to deliver fluoride to teeth in the 21st century,” in a widely-cited 2014 study.

Insider reached out to several different obstetricians across the US to ask for their advice on the new study, but none of those who responded wanted to comment on this new study and how it might change their recommendations for pregnant women. The American Academy of Pediatrics still recommends that children across the US “drink fluoridated tap water.”

Fluoride’s benefits and risks are still being studied

Both Trasande and the editor of JAMA Pediatrics (the journal behind the new study) said that this won’t be the last word on water fluoridation. In an editorial published alongside the study, Harvard public health expert David Bellinger pointed out that it wasn’t so long ago that the idea minor lead exposures might be dangerous for developing brains ” was bitterly contested in the 1980s and 1990s.”

“It was only the weight of evidence that eventually accumulated that led to the now widely held consensus that no level of lead exposure is safe,” Bellinger wrote.

Trasande agreed, saying science always “continues to evolve.”

“This study is doing its job because it’s raising important questions about old paradigms,” he said. “We may have done things to the population in the past with good intentions that may not have the expected impacts, or the ones we thought they did.”